Methods and systems for continuously detecting a state of contact or non-contact between a tip of an instrument and a writing medium of variable thickness are known.
It is known practice to use a writing instrument bearing a contact detection device such as a pressure sensor, but such a writing tool needs to be provided with an electronic device employing an electrical power supply source.
It is also known practice to use a touch-sensitive writing surface, such as a touch interface, but such an approach does not allow passive media of variable thickness, such as a notebook, to be used.
It is also known practice to use a fixed contact threshold, for example as described in document FR 2988874, which does not allow faults in estimating the position of the tip of the writing instrument to be overcome, requires a submillimetric estimation error and is ineffective if the writing medium is deformed on contact with the instrument.